High tensile strength magnesium aluminum silicate glass compositions



o e i 3,139,471 HIGH TE SllLE STRENGTH MAGNESIUM ALUMI- NUM SILICATE GLASS COWGSITIQNS George L. Thomas, Par-ma, Ohio, assignor to The B. F.

Goodrich Company, New York, N.Y., a corporation of New York No Drawing. Fiied May 11, 1962, Ser. No. 194,156

6 Claims. (Cl. 106-50) This invention relates to a magnesium aluminum silicate glass composition to be usedprincipally for glass fibers. The glass composition of this invention has fiber spinning properties comparable to a sodium calcium silicate glass and also to the borosilicate glass composition commonly known in the trade as E glass, yet, fibers spun from this new glass composition have an average tensile strength of at least 30% to 60% greater than the tensile strength of E glass fibers of corresponding gauge.

Because of this substantial improvement in tensile strength, fibers made from the glass composition of this invention are especially useful for the manufacture of glass reinforced plastic articles and particularly filament wound glass-plastic pressure vessels. Moreover, resinglass composites of these high strength glass yarns have been found to be at least 30% to 50% better in tensile strength than corresponding identically processed resinglass composites of E glass yarn.

The glass compositions disclosed can be melted at 2600 F. to 2700 F., formed into marbles and drawn into fibers by conventional methods. Fibers formed from my new glass find ready application in articles where a high strength to weight ratio is important. Pressure bottles and tanks to hold liquids and gases, particularly under high pressures, are widely used in aircraft to store oxygen, hydraulic fluid, deicing fluid and the like, and any new material which will'make a stronger article for the same weight, or a lighter article with the same strength as can be made with presently used materials finds ready interest and acceptance.

While I have succeeded in making a glass composition of extremely high tensile strength, my glass composition also has good spinning characteristics for drawing into continuous filament glass. It has a long working range of approximately 250 F. which is necessary for commercial processing.

My new glass exhibits a Youngs modulus of about 13 l0 p.s.i. in the uncompacted fiber which is an impressive increase over the modulus of commercial continuous filament fiber glass which is about 11 l0 p.s.i. A high modulus or stiff glass is desirable when thefibrous glass is to be used for plastic reinforcement.

This glass has liquidus temperature lower than 2300 F., so that it can be spun under ordinary spinning conditions without the use of special nozzles, cooling or handling. It shows little tendency to devitrify under spinning conditions.

The great strength of my glass is believed to be due to its composition. A glass with high tensile strength, long spinning range, low liquidus temperature, slow rate of crystallization and increased Youngs modulus may be made in the following composition range.

Ingredient: Proportion SiO 50.0 640 Li O 0.1-3.0 A1 18.0-3 0.0 MgO 110-23 .0 B 0 0.0-4.9 Sb O 0.0-1.0- Fe O 0.01 .0

- United States Patent 0 ice As is common in glass technology, the ingredients are given above in terms of oxides of the elements. The compounds'may be added to the glass batch in several diiferent forms, however. Lithium may be added as carbonate, as can magnesium for example.

Silica is an essential component of this glass since it is the glass forming oxide. A small amount of B 0 is preferred in this glass composition, and in the amount in which it is used, it is considered to be a fluxing and refining agent, not a glass forming oxide. When B 0 is added to the glass, the strength is improved over that of a glass with no B 0 The preferred B 0 content is about 0.4% to 3.5%, but glass with tensile strengths greater than those for comparable E glass can be made with amounts of B 0 up to about 5% and as low as a trace, or even 0%.

The alkali oxide is employed as a flux in the glass. Lithia has a small ionic radius and relatively high field strength for alkali ions. Experiments have shown that in these magnesium aluminum silicate glasses the preferred Li O content is between 0.5% and 2.5% but glasses of relatively high tensile strength compared to E glass have been made using amounts of lithia both slightly above and below these limits. Soda (Na o) and potassium oxide may be used in combination with lithia or alone to lower the materials cost of the glass and to help the fiuxing properties, but best results are obtained with lithia alone.

A very common ingredient'of silicate glasses is CaO. It generally contributes to stability and durability of the glass, serves as a flux and helps to lower viscosity and increase fluidity of the glass batch. I have discovered that in the glasses of this invention, calcia is detrimental and is preferably not to be used at all. It tends to lower tensile strength .and modulus of elasticity and to raise V the liquidus temperature.

Magnesia is required to reduce viscosity and avoid devitrification of the glass batches. A high alumina content contributes to durability, but in glass with high alumina it is hard to introduce magnesia in the absence of calcia because the glass is stiff and requires very high melting temperatures. These conditions can lead to stones in the glass caused by the magnesia and the glass will have a tendency to devitrify. The addition of iron oxide helps to dissolve magnesia in high alumina glass in the absence of calcia. The combination of magnesia and iron oxide gives the glass a long working range and allows spinning from commercial spinning units to form continuous filament glass fiber.

Antimony oxide improves homogeneity of the glass by aidingmixing early in the melt period, reduces gas bubbles and acts to improve the working properties of the glass.

The high alumina content of this glass is believed to be.

important in the attainment of the high tensile strength developed. Incorporating such high amounts of alumina in a glass is diflicult, since it tends to cause devitrification at the low temperatures employed for spinning. The suc-.

A1 0 employed in a silicate system (one which is at least.

50% SiO by weight).

In order to produce the strong glass'compositions of this invention, it is important that I control the Al O MgO'ratio between 1.0 and 2.2. Ratios above and below this range have been found .to produce glasses of lower tensile strengths, although it is noted that even these lower strength magnesium aluminum silicate glasses are as strong as commercial E glass which is the present day standard. i

iMetaphenylenediamine 13 The glass of this invention has a tensile strength superior to that of commercially available filament glasses and an improved Youngs modulus. It melts readily in existing glass melting units, and is easily spun in ordinary platinum type spinning units; 2

To compare various batches ofniy glass with each other and with continuous filament'E glass, I have employeda single filament tensile test as follows: '1 The glassbatch is mixed, melted at 2675 F; in a platinum lined 500 cc. alumina crucible set inside an electrically heated Pereny furnace and formed into cullet. The bullet is remelted at about 2500 F; in .a platinum bush-. ing'and drawn through the single platinum nozzle. The same nozzle and drawing speeds are employed in all cases. The filament is drawn at the rate of 5,000 feet per cut from the section between the nozzle and the drawing cardboard containing 5 one inch openings along the length of the filament. The filament ends overlapping the end of the cardboard are removed and checked for diameter under a microscope. inch. The filament is glued to the cardboard at the end minute; and a length of approximately of filament is 7 method is described in 1. App. Physics, 20, 49 3 01949).

wheel during spinning. The sample is mounted on a V They should agree within 0.00002 4' The resin'is applied by running the finish coated yarns through a container of resin at room temperature.

a standard sonic method utilizing measurement of the a speed of a sound transmitted through the" glass. This The glass composition of my invention is illustrated by the following examples wherein the ingredients are proportioned by weight.

EXAMPLES I-X Y Batches were mixed accordingito the-following oxide compositions, melted in a small 200 lb. capacity day tank at 2.675 F. and formed into marbles. The marbles were remelted in platinum bushings and drawn into both single filament and 204 filament form. The two typesof filaments were processed as described above. Glass composiof each opening and the cardboard is cut transversely to 'tions and test data are summarized in Table 1. Standard the filament between the openings. to give '5 one inch E glass was employed as the control.

Table 1 V V Oxides Ex.I Ex. 1r 1 Ex. HI .ExIv Ex.V Ex. v1 Ex..VII Ex; VIII Ex. IX Ex.X

510:, percent 62.7 59.3 61.1 53.3 r 54.8 61.2 54.7 53.7 55.3 53.6 Li O,percent .12 0.4 1.24 1.3 2.0 1.3 2.0 1.3 1.3 3.4 A1203, percent 18.6 20.0 19.4 24.2 28.7 23.7 21.0 11.0 23.1 27.4 MgO,percent 14.6 16.4 15.2 12.8 13.0 12.5 19.6 26.0 12.2 12.8 1 1310;, percent... 1.8 2.0 1.86 2.2 1.0 0.1 2.7 2.0 6.4 2 51110 percent- 0.6 0. 5 0.7 0.7 0.5 0.7 0.5 0.7 FegQrpercent. 0.5 0.5 10.5 0; 0.5 0.5 0.5 Al O3/MgO, percent. .2s a .27 1. 21 1. 88 2. 20 1. 88 0. 9 2. 1.88 2. 14 Liquidus temp., F 2,240 2,320 2,260 2,320 2,330 2,250 2,370 2, 260 Average'single filament tensile strength,

p.s.i. X 10 E glass=400 639 590 635 663 541 574 508 518 518 494 Average 204 filament tensile strength epoxy resin coat, p.s.i. X 10 E g1ass=345 425 437 448 lengths of filament which can be mounted in an Instron Examination of Table 1 shows that when glass composi- Testing Machine for tensile test. With every group of tions are-made from the specific materials and in the experimental filaments a control group of commercial E specific ranges and combinations of those materials that glass filaments is run. a p I have suggested, filament glass of much greater strength In another evaluation test for the glass fibers, a 20-4 than B glass is obtained. In Examples I-VI, average filament yarn is prepared, coated with a resin compatisingle filament tensile strengths of 135% to 166% of that ble finish, dried, twisted, coated with an epoxy resin, of E glass were developed. In the epoxy resin coated glass andbroken in tension onthe Instron Tensile Testing Mayarns, my glasses developed strengths equal to 12.3% to chine. In making the yarn the glass marbles are melted 130% of that of E glass. at about 2500 F. and spun from a 204 hole platinum Examples VII and VIII illustrate that Al O /MgO bushing. At'a point about 4 feet below the nozzles where ratios above and below the critical range of 1.0 to 2.2 give the filaments converge to form a roving, the finish is a pglasses materially weaker than the favored glasses, but. plied byrunningthe glass filaments over a finish imstill stronger than comparableE glass. pregnated felt pad at 7000 per minute. The roving is Example IX shows that increasing the amount of boric dried in an oven for about 5 hours at 180 F. The dried, oxide above*4;9%, the amount where it ceases to be a finish-coated roving is then given a twist of one turn per refining agent and becomes a glass former, does not pro inch. Now the material is called yarn. duce the very high strength glass of my invention. The resin compatible finish applied to'the glass yarn Example X shows that too much Li O in the glass tends "consists of: p to detract from thetensile strength developed in the con- ,Gamma-aminopropyltriethoxy silane ,l-.. 450 i fiiament form 162% solids mixture of parts polyvinyl actetate 0 I 7 +35 parts polyester plasticizer believed to be dis- 7 A ass composmon amp i B203: as a for Solved in methylethyl ketone 2.800 I igh tensile strength glass fiber cons st ng of, I56% solids polyvinyl acetatebelievedt-o be disr i solved in methylethylketone 'ml 4000 65 3 8 i "f-"f 3 153 W 36 A1 0 4. 18.0-30.0 5 'I -e epoxy resin applied to the-finish coated glass yarn MgO 11,0 30 consists of: a j B 0 -g 0.0-4.9 i r Parts 70519 0, '0.-0 1.0 Epoxy resin (diglycidal ether of bisphenol A, mol wt. Fe O 0.0-1.0

360-380) 90. V p 1 a 4 a frEpoxy" resin (diepoxy resin with mol wt. of 9 50 to parts by weight with the ratio Al O /MgO in the range 11150 and low'numlbe'rof cross links per molecule)- 110 of 1.0-2.2, said fiber having a tensile strength from about 541,000 to 663,000 p.s.i.

The resin is then cured in an oven'at 200 F. for about 2 2. A glass composition, employing B as a flux for high tensile strength glass fiber consisting of:

Percent SiO 62.7 Li O 1.2 A1 0 18.6 MgO 14.6 B 0 1.8 Sb O 0.6 Fe O 0.5

said fiber having a tensile strength from about 541,000 to 663,000 p.s.i.

3. A glass composition employing B 0 as a flux for high tensile strength glass fiber consisting of:

Percent SiO 59.3 Li O 0.4 2 3 20.9 MgO 16.4 2 3 2.0 Sb O 0.5 F2O3 0.5 Al O /MgO 1.27

said fiber having a tensile strength from about 541,000 to 663,000 p.s.i.

4. A glass composition employing B 0 as a flux for high tensile strength glass fiber consisting of:

Percent SiO 61.1 Li O 1.24 131 28 i2; 13,0 1.8 6 Sb O 0.7 F203 0.

said fiber having a tensile strength from about 541,000 to 663,000 psi.

5. A glass composition employing B 0 as a flux for high tensile strength glass fiber consisting of:

Percent SiO 58.3 Li O 11.3

6 A1203 24.2 MgO 12.8 B203 2.2 Sb O 0.7 F6203 0.5 Al O /MgO 1.88

said fiber having a tensile strength from about 541,000 to 663,000 p.s.i.

6. A glass composition employing B 0 as a flux for high tensile strength glass fiber consisting of:

Percent SiO 54.8 Li O 2.0 A1 0 23.7 Mg() 18.0 13 0 1.0 Sb O 0.5 lFe2O said fiber having a tensile strength from about 541,000 to 663,000 p.s.i.

References Cited by the Examiner UNITED STATES PATENTS 3,044,888 7/ 62 Provance 10650 3,095,311 6/63 Von Wranau et a1 106-50 3,117,881 1/ 64 Henry et a1 106-39 FOREIGN PATENTS 124,553 6/47= Australia.

765,244- 1/57 Great Britain.

163,590 6/58 Sweden.

OTHER REFERENCES Osborn et 211.: Phase Equilibrium Diagrams of Oxide SystemsPlate 3- MgOAl O SiO published 1960 by American Ceramic Society, Columbus, Ohio.

Lajarte: German application, 1,088,675, printed Sept. 8, 1960 (K1 32bl), 4 pages spec.

Karkhanavala et al.: Reactions in the System Li O-- MgOAl O SiO I, The Cordierite-Spodumene Join (page 3 94), J. Amer. Cer. 800., Dec. 1953.

TOBIAS E. LEVOW, Primary Examiner. 

1. A GLASS COMPOSITION, EMPLOYING B2O3 AS A FLUX, FOR HIGH TENSILE GLASS FIBER CONSISTING OF: 